[Lwio]

Sorry if this was answered before, I tried searching.
I have a kindle, keyboard version.
When going to read a book the loading symbol, I think it's a loading symbol, top left corner, appears.
The symbol animates i.e. a circular arrow thing. The symbol then stops spinning and remains on the screen. On another kindle we own the symbol doesn't remain.
The symbol remains on screen on each page and in other books.
Tried restarting, holding the power switch for 20 secs, no change.
Some books are store bought some are loaded via Cailbre. The symbol remains on both types.